This invention relates to pipe scribers and more particularly to a novel pipe joint intersection contour scriber for use in the art of welding pipes together at intersections which may or may not be perpendicular.
In the art of welding pipes together at intersections which may or may not be perpendicular, the end of a branch pipe at such an intersection will define a rather complex curve, and it is necessary to scribe this curve with an appropriate portable tool so that the pipe may be cut at the appropriate place and welded to the mating pipe so that the intersection is even with the pipe to which it will be connected.
It is known in prior art devices to provide such portable tools for accomplishing the scribing and/or cutting and such prior art devices are disclosed in a number of patents uncovered as a result of a prior art search. The patents uncovered are the U.S. Pat. Nos. 2,389,286; 2,545,666; 2,726,450; 2,852,847; 2,859,522; 3,464,685; 1,858,076; 2,878,010; and 3,442,500.
Of particular interest to the applicant's invention are the above patents herein discussed below as follows:
1. U.S. Pat. No. 2,545,666 issued to H. E. Lonngren and entitled "Pipe Intersection Bevel Cutting Device" discloses a device having a flame cutter or torch 19 rigidly connected to a rotatable guide assembly so that it may be rotated completely around a branch pipe. The path of the torch is diverted longitudinally as it turns by wheel 26 rolling along a cylindrical template 24 which has the same diameter as the main pipe 8 to which the branch pipe is to be connected. A second torch 18 is likewise guided by the same mechanism to cut the corresponding hole in main pipe 8 for accurate mating of the two pipes. This patent is apparently utilized only on "T" branch connections and requires a centering plate 32 and collars 33 to match the outside diameter of each branch pipe used. In addition this device requires contoured template elements 24 for each size of branch and in the event the device is not restricted to "T" connections, a template contoured for each desired angle of intersection would be needed for each size of branch pipe. The cylindrical template 24 also becomes cumbersome when mating a 4" pipe branch to a vessel having a diameter of 36" for example.
2. U.S. Pat. No. 2,878,010, issued to A. Cink and entitled, "Hand Apparatus for Flame Cutting of Profiled Tube Ends" operates in a similar manner to that of the above-mentioned Lonngren patent although it has a somewhat different configuration. The internal mounting utilized in this device is branch size range limiting and is not specific as to adjustability of one template with respect to inclination. There appears to be no means of determining the angle of inclination of one template without the need for others.
3. U.S. Pat. No. 2,852,847, issued to C. H. Cast and entitled, "Pipe Intersection Delineating Apparatus" teaches the use of a variable sleeve 30 on which a scribe is mounted so as to rotate about a pivot pin 2 and mark the proper cut line for a pipe intersection. The displacement of the scribe relative to the pivot corresponds to the radius of the main pipe. The orientation of bracket 21 corresponds to the angle of intersection. This device does not delineate mitered intersections and requires a shifting of the scribe-pointer bracket to obtain a complete delineation of a pipe intersection. In addition it requires sleeves and/or shims to accommodate mounting of the apparatus to different size branches.
4. U.S. Pat. No. 2,859,522, issued to C. M. Thomas and entitled, "Pipe Marker" discloses a device with a principal of operation similar to that of the before-mentioned Cast patent but requires a repositioning of the apparatus to complete delineation and further requires a determination of a center line on the branch pipe with the unit being not self-centering. The device shown in this patent would probably be cumbersome and inaccurate when used with smaller branch pipes and does not delineate mitered intersections.
5. U.S. Pat. No. 2,389,286, issued to W. W. Watkins and entitled "Apparatus for Marking or Cutting Pipes" discloses a device for cutting or marking pipes to be joined at their ends and has a cutter or marker which is guided along the pipe in a plane which may be oblique with respect to the pipe end. This device is not self-centering and makes only mitre cuts of delineations and the chocks on the end of the pipe waste a portion of the work piece.
The remaining patents before mentioned are not felt to be particularly pertinent and have been listed for general information concerning the level of development in the general arts area.